The present invention relates to plasma processing and more particularly to monitoring material buildup on system components in a plasma processing system using an optical monitoring system.
The fabrication of integrated circuits (IC) in the semiconductor industry typically employs plasma to create and assist surface chemistry within a plasma reactor necessary to remove material from and deposit material to a substrate. In general, plasma is formed within the plasma reactor under vacuum conditions by heating electrons to energies sufficient to sustain ionizing collisions with a supplied process gas. Moreover, the heated electrons can have energy sufficient to sustain dissociative collisions and, therefore, a specific set of gases under predetermined conditions (e.g., chamber pressure, gas flow rate, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being performed within the chamber (e.g., etching processes where materials are removed from the substrate or deposition processes where materials are added to the substrate).
Although the formation of a population of charged species (ions, etc.) and chemically reactive species is necessary for performing the function of the plasma processing system (i.e. material etch, material deposition, etc.) at the substrate surface, other component surfaces on the interior of the processing chamber are exposed to the physically and chemically active plasma and, in time, can erode or become coated with deposits. The erosion or coating of exposed system components in the plasma processing system can lead to a gradual degradation of the plasma processing performance and ultimately to complete failure of the system.
Various parts of a plasma processing system consist of consumable or replaceable components that are fabricated from silicon, quartz, alumina, carbon, or silicon carbide, for example. Examples of consumable system components include electrodes, shields, rings, baffles, and liners. The consumable nature of the replaceable components can require frequent maintenance of the plasma processing system. This frequent maintenance can produce costs associated with plasma processing down-time and new plasma processing chamber components, which can be excessive.
Consumable parts are commonly cleaned or replaced after detrimental processing conditions or processing results are observed. These adverse processing conditions can include plasma arcing, particle formation, variations in substrate etch rate, etch selectivity, and etch uniformity. Alternatively, consumable parts can be cleaned or replaced according to a predetermined maintenance schedule that can, for example, be based on the number of plasma operating hours. These methods can result in overdue or premature replacement of consumable system components.
A plasma processing system is provided that allows for monitoring material buildup on system components during plasma processing. The plasma processing system comprises a processing chamber and an optical monitoring system for monitoring light emission from the processing chamber. System components are provided that can contain at least one emitter that is capable of fluorescent light emission when exposed to a plasma.
A method is provided for monitoring material buildup on system components in a plasma processing system. The system components can contain at least one emitter that can produce characteristic fluorescent light emission when exposed to a plasma. The method utilizes an optical monitoring system to monitor the fluorescent light emission.
Monitorable consumable system components are provided that can contain at least one emitter that can produce characteristic fluorescent light emission when exposed to a plasma. The emitters allow for monitoring material buildup on the consumable system components.